The present invention relates to an inspection pattern formed on a semiconductor wafer for detection of a latent defect of a multi-layer wiring structure of a semiconductor device (that is, for quality inspection of a metal process of a semiconductor device). The present invention also relates to a semiconductor device including the aforementioned inspection pattern, an inspection method of a semiconductor device using the aforementioned inspection pattern, and an inspection system that implements the aforementioned inspection method.
FIG. 28 is a schematic vertical cross-sectional view showing a multi-layer wiring structure of a semiconductor device. In the multi-layer wiring structure of FIG. 28, a contact hole (which is also referred to as a “via-hole” or a “through-hole”) 13 filled with a metal (e.g., a tungsten (W) plug) 14 is provided in an insulating layer 19 between the upper-layer wiring portion 11 and the lower-layer wiring portion 12 that are made of aluminum (Al), for example. The contact hole 13 establishes an electrical connection between the upper-layer wiring portion 11 and the lower-layer wiring portion 12. In the following description, the contact hole 13 filled with a metal is referred to as a “contact portion” or a “via”. A multi-layer wiring structure including a plurality of upper-layer wiring portions, a plurality of lower-layer wiring portions, and a plurality of contact portions electrically connecting the upper-layer wiring portions and the lower-layer wiring portions alternately in series is referred to as a “contact chain” (which is also referred to as a “via-hole chain” or a “through-hole chain”).
In the forming process of the tungsten plug 14, an adhesion layer made of a high melting point metal such as sputtered titanium nitride (TiN) is formed on the lower-layer wiring portion 12. For the purpose of removing an oxide 15 formed at the bottom of the contact hole 13 (i.e., on the lower-layer wiring portion 12), prior to the formation of the TiN adhesion layer, the lower-layer wiring portion 12 is generally subjected to the cleaning sputtering process. However, there occurs a case where a process abnormality makes it impossible to remove the oxide or causes the oxide to partly remain in the contact portion.
When the oxide cannot be removed at all, the resistance of each contact portion (including its connection parts) will increase extremely or each contact portion will fail to be conducted. Thus through a continuity test or the like for the contact portion, a remarkable defect or failure resulting from a process abnormality can be detected. Further, when the oxide partly remains at all the contact portions in the contact chain, the entire resistance of the contact chain will increase. Thus a defect or failure resulting from a process abnormality can be detected by measuring the resistance of the entire contact chain.
However, when the oxide partly remains only in any one or some of the plurality of contact portions in the contact chain, it is difficult to detect a defect by a continuity test of the contact portion or by measuring the resistance of the entire contact chain. This is because an increase in the resistance or resistances of one or some contact portions alone is very small when compared with the resistance of the entire contact chain and is indistinguishable from fluctuations of the resistance of the entire contact chain.
As described above, there may be cases where a process abnormality causes the increase of the resistance or resistances only in random one or some parts of the contact chain, which is very small when compared with the resistance of the entire contact chain. The defects resulting from such process abnormality include a defect in an interface 15 between the tungsten plug 14 and the lower-layer wiring portion 12, a void (or a cavity) 16 in the tungsten plug 14, a defect in an interface 17 between the tungsten plug 14 and the upper-layer wiring portion 11, a defect 18 existing in the wiring portion 11 or 12, and a degraded metal coverage (i.e., a coverage defect) The defects may possibly be generated in any position within the contact chain.